1. The Field of the Invention
The present invention broadly relates to improved apparatus for indicating a line, and in a preferred embodiment, to apparatus for indicating a plurality of lines, each of which is capable of being separately moved and rotated. In another embodiment, the invention is concerned with apparatus for producing and visually displaying one or more images of a line indicator or indicators.
2. The Prior Art
The large amount of equipment and material needed in the traditional navigation of aircraft and watercraft by manual techniques results in substantial expense to the operator. For example, the navigational aids used by a navigator in manual plotting may include an inventory of numerous paper or cloth mounted charts of substantial size, a chart table large enough to provide a working surface therefor, transparent overlays for the charts, parallel rules, straight edges, dividers, protractors, lead pencils, grease pencils and pens. It is costly initially to buy such a large amount of equipment, and it is also costly to provide the auxiliary equipment and facilities necessary to use the equipment and maintain it in good condition. For instance, sufficient working space must be provided for the navigator to set up the chart table and perform his duties, and storage facilities must be provided when the equipment is not in use. Additionally, some provision must be made for navigation during storms, and often special foul weather gear and equipment is needed.
It is apparent from the above that navigation by traditional manual means requires a large amount of space, and thus usually is not practical when navigating small private airplanes and pleasure boats. The economic factors also must be given consideration and especially with small privately owned aircraft and boats where expenses must be kept under control. Even with the larger craft and where expense is not a problem, the amount of space available to the navigator is very limited and it is difficult for the navigator to perform his duties.
The primary purpose of traditional navigational charting or plotting is to allow the navigator to determine his position on an appropriate chart by manually drawing or plotting thereon one or more lines-of-position. Such lines-of-position may be obtained from traditional sources such as celestial fixes, polaris sightings, radio direction finder bearings, radar, Loran, and by visual bearings of known points on the chart. One line-of-position often is not sufficient to allow the navigator to accurately determine his position, and usually it is necessary to manually plot on the chart surface or transparent overlay at least two, and preferably at least three, lines-of-position. This procedure is time consuming under the best of working conditions. Moreover, the working conditions available to the navigator often are not adequate, and this tends to further increase the amount of time required as well as the accuracy of the results. In instances where the aircraft or watercraft is moving rapidly, it is desirable that the lines-of-position be obtained and plotted in the shortest practical period of time in order to obtain an accurate fix. This is not possible in many instances when using the traditional prior art equipment and manual practices.
It is apparent from the foregoing that the art has long sought a small reliable navigational device which assures rapid and accurate navigational plotting in a confined space under both good and bad weather conditions, and which is also inexpensive to buy, operate and maintain. My U.S. Pat. No. 3,865,477, issued Feb. 11, 1975, the disclosure of which is incorporated herein by reference, discloses and claims a navigational device which overcomes many of the aforementioned problems of the prior art. Nevertheless, further research in this field has resulted in additional improvements which are embraced by the subject matter to be disclosed and discussed more fully hereinafter. Such further improvements are especially useful in navigating with prior art apparatus having means to visually display a chart image, including the navigational device disclosed in U.S. Pat. No. 3,865,477. These improvements also are useful in navigating with a conventional paper or cloth-mounted chart.